In general, Digital Rights Management (DRM) is a general resource protection technique by which illegal copy and illegal use of digital resources are prevented so that only legitimate users can use the digital resources. The DRM provides an overall protection framework throughout production and distribution of the digital resources. For example, in the DRM, a digital resource is converted to data which is encrypted in a packet format by using an encryption technique so that the digital resource cannot be used without a legal authentication process.
By interacting with a variety of resource service models, the DRM has become a foundation for a reliable and legal resource service. Currently, in practice, a service provider uses a unique DRM to protect its own resource. For example, in a case of a music-source service for providing a music source through on-line communication, the music source is encrypted in a specific encryption pattern to prevent illegal copying, and thus the music source can be reproduced only by the use of an application provided by a corresponding service provider.
However, due to technical and political closure features of the DRM, interoperability is generally impossible between different DRMs. Therefore, a resource provided by one service provider cannot be used with an application provided by another service provider. This has been noted as an important problem which actually restricts a general-purpose use of a DRM resource and thus obstructs the spread of markets for legal contents.
Recently, to deal with the above problem, there is an attempt to provide a framework in which the closed DRM structures are compatible with one another, and a representative example thereof is a DRM interoperable system. The DRM interoperable system may be a system which intermediately controls different DRMs so that a resource or a license can be exchanged to be used.
The DRM interoperable system is implemented by defining system resources and by forming operation models which generate and manage the defined system resources. In particular, it is regarded that critical factors in the implementation of the DRM interoperable system include reliable authentication and management for a client, effective transmission of a resource and a license, and effective information management.